Electron beam devices, in particular scanning electron microscopes, are used for examining surfaces of objects. To do so, with a scanning electron microscope, an electron beam (hereinafter also referred to as a primary electron beam) is generated by a beam generator and focused by a beam guidance system on the object to be examined. The primary electron beam is guided by a deflecting device in a grid pattern over the surface of the object to be examined. The electrons of the primary electron beam then interact with the object. As a result of this interaction, in particular, electrons are emitted from the object surface (so-called secondary electrons) or electrons of the primary electron beam are backscattered (so-called backscattered electrons). The secondary electrons and backscattered electrons are detected and used to generate an image. This thus yields an image of the surface of the object to be examined. Reference is made here to DE 103 01 579 A1 as an example, which is incorporated herein by reference.
It is also known from the related art that an electron beam device may be used for treating the surface of an object. More specifically, it is known that the surface of an object may be etched, the etching being induced by an electron beam. With the known method, a gas is guided to the surface of the object and is adsorbed by the surface of the object. A reaction of the gas with the surface of the object is induced by the electron beam which is rasterized over the surface of the object, forming a volatile reaction product which is removed by pumping. As an example, reference is made here to the publication “E-beam probe station with integrated tool for electron beam induced etching” (Elektronenstrahlsonden-Station mit integriertem Gerät zum mittels Elektronenstrahl induzierten Ätzen) (Dieter Winkler, Hans Zimmermann, Margot Mangerich, Robert Trauner, Microelectronic Engineering 31 (1996), 141-147), which is incorporated herein by reference.
Furthermore, it is also known from the related art that a scanning electron microscope may be equipped with an ion beam column. Ions which are used for preparation of objects (e.g., polishing an object or applying material to the object) or for imaging are generated by an ion beam generator situated in the ion beam column. For example, it is possible in this way to obtain three-dimensional information about an object to be examined. Therefore, image series are recorded by a scanning electron microscope. Between two images of the image series, the object to be examined is prepared. Three-dimensional models of the object to be examined may be calculated by combining the images of the image series.
All the devices described here have a disadvantage. If a nonconductive object is to be examined or treated by an electron beam, the object develops a charge. This influences in particular the electron beam directed at the object. The imaging of the surface of the object is also influenced. In the worst case, features of the surface of the object are no longer imaged properly.
To avoid this effect, a scanning electron microscope, which is used for imaging objects and is provided with a gas feed mechanism guiding an inert gas to the surface of the object, is known from the related art. The inert gas forms a layer covering the area where a primary electron beam strikes the object. This should prevent or reduce charging of an object.
Furthermore, a system is known from the related art for dissipating charges from samples in scanning electron microscopic examinations. With this system, a gas stream is directed in a targeted manner at an area of an object to be imaged. The gas molecules dissociate there into positive ions and low-energy electrons due to the interaction with the primary electron beam and secondary electron beam. The positive ions are accelerated toward the negatively charged surface of the object to be imaged, where they pick up electrons from the surface in a neutralization process and are then drawn back away from the surface of the object as a neutral gas.
With regard to the discharge methods described here, reference is made to U.S. Pat. No. 6,555,815 B2 and DE 33 32 248 A1 as examples, which are incorporated herein by reference.
Accordingly, it would be desirable to provide a method for examining a surface with the aid of a particle beam, which counteracts the charge buildup on an object to be treated in a particularly effective manner. Furthermore, it would be desirable to provide a particle beam device which is suitable for performing the method.